1. Field of the Invention
This invention relates to a system for detecting the presence of chemicals whether they be in liquid, vapor or gaseous state. More particularly the system detects hazardous chemicals such as gasoline, trichloroethylene, alcohol, and other solvents and hydrocarbons. The system is particulary useful in detecting leakage of such chemicals, as well as others, from tanks into surrounding areas where they may contaminate drinking water and the like. The term "chemicals" is used broadly in this patent to indicate the foregoing and similar chemicals.
When the system detects the presence of chemicals, an alarm which may be either audible or visual is turned on.
The system employs a probe to detect the chemical in a double walled tank or in a monitoring well drilled for this purpose next to an underground tank, when floating on the water and in other environments. Detection by the probe energizes the alarm system.
Other objects of the invention are that it is safe in the sense that it does not cause fires or explosions and is relatively inexpensive. The probe has no moving parts and requires only a single length of wire rather than a collapsible length which is required in other floating probes.
2. Description of Related Art
Kashikawa U.S. Pat. No. 3,970,863 discloses a petroleum leakage detection system comprising an S-B-S block copolymer which is made electro-conductive by coating or filling it with a conductive metal powder, foil or the like. When a petroleum product comes in contact with the copolymer, the latter swells, thereby separating the dispersed metal and causing a decrease in conductivity. The disclosure of Kashikawa is the use of an S-B-S block copolymer which swells. The present invention operates by a change in conductivity of the copolymer as a result of changes in the conductivity of the materials rather than the spatial separation thereof.
Luden U.S. Pat. No. 3,579,097 discloses an ammonia gas detecting system comprising a non-porous, non-conductive probe coated with a liquid film. When ammonia is absorbed by the film, the conductivity is changed and is detected. Thus this reference works only for gases which are readily absorbable into a liquid film and then affect the conductivity thereof. Luden does not disclose a polymer material such that its conductivity is increased when gas is absorbed. In the present invention the conductivity of the copolymer is decreased.
Hsu U.S. Pat. No. 3,562,731 discloses a water detecting system which includes an alarm but is otherwise different from the present invention.
Hedeby U.S. Pat. No. 1,786,843 shows a time clock for a pipe leak detector system which is activated once the leak is detected.
Other patents showing detecting hazardous gases or liquids wherein the conductivity of an element is monitored include U.S. Pat. Nos. 2,716,721; 2,760,152; 3,262,106; 3,720,797; 3,966,580; 3,992,267 and 4,145,913.